Billing with GUI and OpenSER GUI

I am looking for a hibernate of the portaONE sip switch that comes with their billing system, but don't need it to be nearly as sophisiticated as their system. For our hosted PBX's

A billing/customer system that keeps track of calls and corresponding charges; redundant system architecture (dual database) should be incorporated. I need to be able to manage wholesale minutes and have a pool of VOIP providers that provide me with different rate cards.

Essentially OpenSER with GUI and a billing system with a GUI, based on the Session Initiation Protocol (SIP), providing a full array of call routing capabilities as well as a solution to the NAT traversal problem. Need various modules such as LCR installed for OpenSER.

Need to have the ability to put different VOIP providers within the system and track/monitor the activity of each provider so I will know if calls made by certain providers fail

-need least-cost routing

-gui to change or add accounts trunk

-manage all aspects of any/all functions that we will use from the gui

-global billing and billing for individual accounts

-billing stats needs to have daily, weekly, monthly, etc..

-stats should be retriveable directly from the database

-would like to have as many billing options as possible

-require fail-over feature so if one provider fails it will automatically switch to the next provider